Not Applicable.
Not Applicable.
1. Field of Invention
The invention is generally related to material hoppers and more specifically to hopper flow and discharge promoters.
2. Description of the Related Art
The prior art of the field of hopper flow and discharge promoters includes varied efforts to improve the process of unloading the contents of a hopper. Problems with the process of uniformly moving materials out of a hopper include arches, ratholes and other types of plugging.
Arches form when particles compact together and, being supported on a number of sides, become stable enough to support the weight of the material stored above. Arches interfere with or terminate material discharge from the bottom of hoppers. If and when they collapse, arches can result in a significant shift in material mass, causing an assortment of harms such as material supply surges, product flooding and equipment damage. Each particular material possesses a critical arching dimension, designated as BC, which typifies a span over which that the material can arch in a circular conical hopper.
One method to prevent arching is to have the opening at the bottom of the hopper larger than the given material""s critical arching dimension. However, processing applications typically require some degree of controlled feed into an aperture of reduced size, limiting the extent to which the opening at the bottom may be enlarged.
Ratholes are caused by uneven lateral pressure through a mass of particles. Walls of a bin that are not sufficiently steep provide lateral support to adjacent matter, allowing this material to cling to the sides. When an opening in the bottom of the bin allows flow, the material under lesser lateral pressure flows out first, creating a tunnel through the mass of material. Typically it is the material in the center of the bin, positioned over the bottom opening that consistently flows down the rathole through the rest of the material. A replenishing supply, typically from the top, refills the rathole. This recently added material then feeds out next, before the older material along the sides. Accordingly, the fresh material going down the rathole is used while the material along the sides of the hopper ages. Materials that lose their suitability after a period of time can deteriorate while stuck on the sides of the bin to the point of being unsuitable. When they finally come loose the quality of the resulting products will be unpredictable. If the material along the sides dislodges suddenly, it can constitute a substantial shift in mass, also causing a myriad of harms, to include material supply surges, product flooding and significant equipment damage.
The required angle of wall steepness to prevent material from clinging to the sides, referred to as the release angle, is dependent on the particular characteristics of the specific material to being handled, and is referred to as xcex8C. This release angel overcomes the cohesive strength of the material and the bin wall. In conical bins, this angle can be as high as 80 degrees. Since high angles require great heights to achieve useable capacities, low angle walls of 45 degrees or less are desired. Bins with 60-degree walls are used when materials have hang-up problems. Since users are constrained by their capacity requirements and their height limitations, called headroom, product flow problems frequently occur when materials possess a high xcex8C.
The quest for increased volume, minimal height and uninterrupted flow run contrary to each other. At a set wall angle, denoted as xcex8, an increase in height increases volume. But volume is substantially reduced as the angle of the wall increases. The extra slope, rather that storage area, expends increased the height. This means that decreases in the wall angle, even minor ones, can make substantial increases in volume or decreases in required headroom for a specific volume.
Active and passive measures are employed to avoid flow problems. Active measures to induce smooth, complete material flow include vibratory, mechanical and matter-induced. These methods have been used individually or in combination.
Vibratory measures, as in U.S. Pat. No. 5,960,990 issued to Radosevich on Oct. 5, 1999, consist of inducing motion into the hopper structure in the attempt to prevent the material from forming stable structures. Vibration arrangements entail the initial cost of equipment and maintenance of equipment excessive wear by the vibratory process. Manual vibration is sometimes induced by hammering on the outside of the hopper.
Mechanical means primarily consist of paddles, as in U.S. Pat. No. 4,399,931 issued to Maddalena on Aug. 23, 1983, scrapers, as in U.S. Pat. No. 4,129,233 issued to Schmader on Dec. 12, 1978, or structures internal to the hopper, as in U.S. Pat. No. 5,960,990 issued to Radosevich on Oct. 5, 1999.
Matter-inducers, typically using air or some suitable fluid, introduce matter into the hopper with varied degrees of force. Aeration pads, as in U.S. Pat. No. 6,205,931 issued to Degutis et al on Mar. 27, 2001, positioned along the sides of the hopper add air to the material, fluidizing the layer along the side of the hopper, reducing the friction and promoting flow. Forceful air or fluid systems, as disclosed in U.S. Pat. No. 5,628,873 issued to Johanson et al on May 13, 1997, blast the material off the sides or over-pressure the entire hopper, jarring the material out of its stable position.
Passive measures include altering the design of the hopper and controlling the temperature and moisture content of the material. The primary passive measure used in the field is to contour the interior interface of the hopper so as to deny a support structure upon which the material can settle or adhere. The result is a variety of exotically shaped bins, with multiple vertical sections. A prominent example of such designs is U.S. Pat. No. 4,958,741 issued to Johanson on Sep. 25, 1990, which employs multiple structural sections of successively smaller diameter, possessing alternating round and oval openings. These methods have reduced material flow problems. Such units require wall slopes steep enough to cause flow at the hopper walls.
It would be an improvement to the art to provide for a hopper design that incorporates mass flow characteristics and arch breaking configurations in order to maximize capacity in a low-profile design.
The circumference of the outlet orifice is typically an impediment to flow from a hopper, as the outlet orifice is the most constrained point in a hopper. It would also therefore be an improvement to the art for a design to provide a mass flow arch breaking outlet configuration promoting terminal uniform first-in/first-out (xe2x80x9cFIFOxe2x80x9d) flow of material from a hopper, as well as improving the ratio of hopper volume to outlet size.
This invention is a flow promoter for use in material storage or process hoppers for either or both the main body of the hopper and the terminal outlet region of a hopper. The flow promoter can serve as the hopper or outlet housing, or be adapted as a lining component, inserted into existing devices.
This invention provides a flow promoter that induces flow of stored material over a relatively broad area in relation to outlet orifice area. Such induction is provided by a unique surface structure and a plurality of peaks and valleys at the inlet of the flow promoter, which surface, peaks and valleys cooperate to induce flow. Particularly, the flow promoter comprises a central cavity core with a plurality of tapered radial lobes. The flow promoter is generally tapered from the inlet end outer circumference toward the central cavity core and the outlet orifice. A plurality of peaks and valleys angularly spaced on the inlet end, between the radial lobes, create angular stress points, breaking up the uniform downward force pattern of the material, and diverting the material toward different sections of the flow promoter configuration.
Accordingly, the objects of my invention are to provide, inter alia, a hopper interface that:
Promotes and supports mass flow in the contained material;
Limits formation of ratholes and arches; and
Provides containment and discharge of a large volume of material with minimal structural height.
Decrease the required outlet orifice size with minimal structural height.
Other objects of my invention will become evident throughout the reading of this application.